Control circuits



March 19, 1946. c os 2,396,688

CONTROL C IRCUIT Filed March 14, 1942' 2 Sheets-Sheet 1 lie/work w Q h .g

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g lNVENTOR fiz/rrayGCms w f W AT'ToRNEY March 19, 1946. M. G. CROSBY CONTROL CIRCUIT Filed March 14, 1942 2 Sheets-Sheet 2 QQ Q QQ Q Q SQ o mukbuv INVENTOR ATTORNEY N m L Patented Mar. l9, W46

CONTROL CIRCUITS Murray G. Crosby, Riverhead, N. Y., assignor to of Delaware Radio Corporation of America, a corporation Application March 14, 1942, Serial No. 434,743 15 Claims. -(c1. 179-1715) This application concerns timing modulation systems and has as its main object provision of a new and improved circuit for applying the potentials. characteristic of drifts in the main generator frequency and/or of wave length modulations on the generated-wave and/or of nonsymmetrical peak swings of the modulating potentials to the reactance tube in a wave length modulation system of the type disclosed in my United States application, Ser. No. 136,578, filed April 13, 1937, Patent #2,279,659, dated April 14,

My invention is applicable to frequency modulation systems, phase modulation systems, and systems having the characteristics of either or both. In the description and claims the terms frequency modulation and wave length modulation are intended to denote phase and frequency modulation, and phase or frequency modulation.

In describing my invention in detail reference will be made to the attached drawings wherein:

Fig. 1 illustrates a wave length modulator of the type involved here and is used to illustrate the purpose of and need -for. my present improved control potential translating circuit, and one embodiment thereof. This figure is similar in some respects to Fig. 1 of my U. S. application, Ser. No. 136,578, Patent #2,279,659.

Fig. 2 shows another embodiment of improved wave length modulators of this type, arranged in'accordance with my present invention. An improvement in each of these modulators resides in.the circuits coupling the wave frequency discriminator circuits and detector to the reactance tube for control purposes. This figure is similar in other respects to Fig. 2 of my above mentioned application.

- In referring to Fig. 1 of the drawings, 10 is an oscillation generator having its grid 9 and anode regeneratively coupled to a tank circuit l3. The generated oscillations modulated in length, as will be described hereinafter, are fed by winding l5, and/or amplitude limiter, and/or frequency multipliers in unit for transmission from aerial 6. The tank circuit I3 is grounded at one end as shown and is shunted by the space between the cathode 25 and anode 33 of reactance tube 20. The anode H is also coupled by a phase shifting network C and R to grid 3| of the reactance tube by the coupling and blocking condenser CB. The network, etc., is such that a phase quadrature relation is maintained between the voltages on the grid 3| and the anode 33 so that current within the tube reaching the anode is out of phase with the anode voltage about 90 to provide the reactive effect in shunt with the tank circuit I3, used for modulation purposes in these circuits.

The reactance provided by tube 20 is controlled at signal frequency by controlling the tube conductance and this is done by the application of modulating potentials to jack 35 and by way of transformer '29 and grid resistor 28 to the control grid 3|. In modulation which is predominantly phase modulation the modulation potentials supplied to the jack 35 are modified in unit 39 substantially inversely in accordance with their frequency.

In order to stabilize the mean frequency of the generated oscillations and/or if desired to provide degeneration, wave energy modulated in wave length is supplied by lead 36 to the grid 38 of a combined oscillation generator and mixer tube 40. In this tube oscillations of substantially constant frequency are generated by means of electrodes 4| and 43, tank circuit 44, and Piezoelectric crystal 45. These oscillations of substantially fixed frequency are mixed in the tube with modulated waves from l3 and the beat frequency energy appears on anode 45 due to the electron coupling in the tube and are set up in the anode circuit 41. The anode circuit 41 is inductively coupled to the tuned circuit 5|] connected to the anodes of the rectifiers 6|] and GI and is also coupled by a condenser 5| to the anodes of the rectifiers and 6|. These connections provide a discriminating circuit which per se is well known in the prior art and needs no description here. It will be noted, however, that voltages in phase opposition are induced from circuit 41 onto circuit 50 and these voltages are applied in phase opposition to the diodes 60 and BI and that these voltages change in phase with changes in the mean frequency of the energy in 41 and also with faster changes such as changes at syllabic and signal frequency. Voltages are also induced by coupling condenser in phase on the diodes 60 and GI. These latter voltages are of substantially constant phase irrespective of changes in the wave length of the voltages at 41. In this manner changes in the wave length of the wave energy generated in circuit I3 are converted into linear amplitude changes in the discriminating circuit and the amplitude variations are rectified in diodes 60 and 6| and produce differential currents which set up potentials across the differentially connected resistors 64 and 6B which are fed by a timing network to the control grid 3|.

One side of the series resistances 64 and 66 is connected to ground and the other side is connected by resistor RI and condenser CI and resistor R2 and condenser C2 to the grid so that the potential on this grid is controlled in accordance with the modulation from 29 and also in accordance with potentials which are passed by rectifiers BI] and GI and the network coupling the output of said rectifiers to grid 3|.

In Fig. 1 of my above identified application the stabilizing potentials and degenerative potentials are both applied by a common time constant circuit from the rectifier outputs to'the reactance tube control electrode. In Fig. 3 of my U. S. application, Ser. No. 312,446, filed January 5, 1940, Patent #2,279,660, dated April 14, 1942, separate connections between the rectifier output and different reactance tube control electrodes are provided, one for the stabilizing potentials and the other for the degeneration potentials.

It may be found desirable to separately control the functions of slow drift of the carrier frequency and the syllabic shiftdue to the unsymmetrical modulating wave or the shifts due to modulation where degeneration is to be used so that different amounts of control on the two functions may be used. This allows a very high degree of control on the slow response circuit which might cause motorboating if the speed of control is comparable to the syllabic frequency assuming for purposes of description that the second function is to control for non-symmetry of the modulation. Then a smaller amount of control may be used for the faster circuit which controls the syllabic shift. To do this the method and means of Fig. 3 of my United States application #312,446 filed January 5, 1940, Patent #2,279,660 may be used. In this arrangement the slow time constant controls one grid 28 of the reactance tube II) and the fast control circuit controls the other grid 3|. The fast control used in application 312,446 is, as pointed out above, normally fast enough for inverse feedback, but if this arrangement is used to correct for nonsymmetry of modulation peaks as disclosed in my United States application #358,385, filed September 26, 1940, Patent #2,315,050, dated March 30, 1943, the time constant would be increased, that is made larger, to be comparable to the syllabic frequency.

The attached Fig. 1 shows another method by which a large value of slow control and a smaller value of faster control may be applied to a single grid of the reactance tube. In this arrangement the voltages derived from the differential output resistances 64 and 66 are impressed on a time constant circuit RI, CI. The voltages set up in RI are also impressed from a tap on RI to a second time control circuit R2, C2. Voltages unaffected by time control elements RI, CI are supplied to R2 and timed by the elements R2, and C2, CI in series and supplied to grid 3| of reactance tube 20. Voltages passed by the slower time constant circuitRI, CI are also impressed by R2 on the grid 3| of tube 20. Since the time constant of units R2, C2 is shorter than the time constant of RI, CI, these latter voltages are not affected materially by R2, C2. Consequently, RI, Cl forms the slow time constant circuit which passes only very slow drifts. R2, C2 forms the faster time constant circuit which passes variations at a rate comparable to syllabic frequency, but with an amount which is somewhat smaller and is controlled by the slider on resistance RI.

The arrangement of Fig. 1 is similar to the aseaeee arrangement of Fig. 2 but differs therefrom in the following respects. In Fig. 2 a separate tube 10 has its electrodes coupled in oscillation generating circuits including a wave frequency stabilizing line H for the production of substantially constant frequency oscillations. These generated oscillations are fed by line I3 to diode rectifier 15 to mix or beat with the wave length modulated wave energy fed to said diode from the modulated generator I0 through line 35. The beat frequency output of I5, which for reasons pointed out in detail in my U. S. application, Ser. No. 136,578, Patent #2,279,659, mentioned above, is of substantially constant amplitude and is fed to the discriminator 41, 5|, 50, etc. as in Fig. 1. In this discriminator all wave length variations are linearly converted into amplitude variations which are rectified in diode detectors 60 and 6| and appear across resistors 64 and 66. Voltage variations of a period higher than the modulation frequency are filtered by condensers 61 and 69 and the remaining potentials are fed to the capacity and resistance network RI-CI, R2--C2, and Bil-C3, and thence to the suppressor grid 18 of the reactance tube along with modulation from transformer 29.

In Fig. 2, provision has been made to feed to the reactance tube potentials characteristic of slow drifts of the transmitter wave length, potentials characteristic of syllable shifts thereof and potentials characteristic of changes thereof at modulation frequency, these latter potentials providing degeneration to improve the linearity of the modulated wave. The manner in which the slow drift control, syllabic shift control, and inverse feedback is fed to the reactance tube from the detectors 60 and BI will now be described. RI-CI and R2C2 function the same as in Fig. l, but R3-C3 is a time constant which is fast enough to pass all of the modulating frequencies so that inverse feedback takes place. The degree of inverse feedbackis controllable by the variation of the sliders on R2 and RI while the degree of control in accordance with potentials of syllabic rate is controllable by movement of the slider on RI. The operation of this means otherwise is as in Fig. 1 and further description thereof is believed unnecessary.

What is claimed is:

1. In a signalling system, a tuned circuit wherein wave energy the wave length of which is to be controlled flows, a reactance tube coupled to said tuned circuit to control the tuning thereof and thereby control the wave length of the wave energy flowing therein, connections for modulating the conductivity of said reactance tube in accordance with signals to correspondingly control the wave length of the wave energy, a frequency responsive circuit for deriving potentials characteristic of slow changes, and of syllable changes, in the wave length of the wave energy, a resistance and a capacity in series, a second resistance and capacity in series connected across a part at least of said first resistance, connections from said first series resistance and capacity to said frequency responsive circuit for applying said derived potentials across said first series resistance and capacity, and connections between said second resistance and first capacity and said reactance tube.

2. In a signalling system, a tuned circuit wherein wave energy the wave length of which is to be controlled flows, at reactance tube coupled to said tuned circuit to control the tuning thereof and thereby control the wave lengthof the wave energy fiowing therein, connections for modulating the conductivity of said reactance tube in accordance with signals to correspondingly control the wave length of the wave energy, means for deriving potentials characteristic of slow changes, syllabic changes, and changes in accordance with signals in the wave length of the wave energy, and a resistive and capacitive network for applying said derived potentials to said reactance tube, said network comprising a first resistance and capacity in series, a second resistance and capacity in series connected to a part at least of said first resistance and a third capacity and resistance in series coupled to a part at least of said second resistance.

3. In a signalling system, a tuned circuit wherein wave energy the wave length of which is to be controlled fiows, a reactance tube coupled to said tuned circuit to control the tuning thereof and thereby control the Wave length of the wave energy flowing therein, connections for modulating the conductivity of said reactance tube in accordance with signal to correspondingly control the wave length of the wave energy, means for deriving potentials characteristic of slow changes, syllabic changes, and changes in accordance with signals in the Wave length of the wave energy, and a resistive and capacitive network for simultaneously applying said derived potentials to said reactance tube.

4. In a signalling system, a tuned circuit wherein wave energy the wave length of which is to be controlled flows, a reactance tube coupled to said tuned circuit to control the tuning thereof and thereby control the wave length of the wave energy flowing therein, connections for modulating the conductivity of said reactance tube in accordance with signals to correspondingly control the wave length of the wave energy, means for deriving potentials characteristic of slow changes, syllabic changes, and changes in accordance with signals in the Wave length of the wave energy, and an adjustable resistive and capacitive network for simultaneously applying said derived potentials to said reactance tube in separately controllable amounts.

5. Means for transferring potentials the frequencies of which fall within, a plurality of ranges from one point to another including, a first resistance and condenser in a circuit excited by said potentials, said first resistance and condenser having a long time constant to pass variations of low frequency, an additional resistance and condenser in series in shunt to a part at least of said first resistance, to be excited by potentials of lesser amplitude, said additional resistance and condenser having a shorter time constant to pass variations of a frequency above the frequency of those passed by said first resistance and condenser, and an output coupled to said additional resistance and said first condenser.

6. Means for transferring potentials the frequencies of which fall within a plurality of ranges from one point to another incIuding, a first resistance and condenser in a circuit excited by said potentials, said first resistance and condenser having along time constant to pass variations of low frequency, an additional resistance and condenser in series in shunt to a part at least of s id first resistance to be excited by potentials of lesser amplitude, said additional resistance and condenser having a shorter time constant to pass variations of a frequency above the frequency of those passed by said first resistance and condenser, a third resistance and condenser in shunt to a part at least of said second resistance to be excited by potential of amplitudes smaller than the amplitude of the potentials exciting said additional condenser and resistance, said third resistance and condenser having a time constant shorter than the time constant of said additional resistance and condenser to pass variations of a frequency above those passed by said additional resistance and condenser, and an output coupled to said third resistance and said first condenser.

'7. In an angular velocity modulation system a network for transferring, from one point to another, potentials the frequency of which fall within a plurality of ranges, a first resistance and condenser in a circuit excited by said potentials, said first resistance and first condenser forming a time constant network of relatively long duration, a second resistance and second condenser in series in shunt to a part at least of said first resistance, said second resistance and second condenser forming a second time constant network of less duration than said first network and an output coupled to said second resistance and first condenser.

8. In an angular velocity modulation system a network for transferring, from one point to another, potentials the frequency of which fall within a plurality of ranges, a first resistance and condenser in a circuit excited by said potentials, said first resistance and first condenser forming a time constant network of relatively long dura-' tion, a second resistance and second condenser in series in shunt to a part at least of said first resistance, said second resistance and second condenser forming a second time constant network of less duration than said first network, a third resistance and condenser in shunt to a part at least of said second resistance, said third resistance and third condenser forming a third time constant network of less duration than said second network and an output coupled to said third resistance and first condenser.

9. In an angular velocity modulation system a network for transferring, from one point to another, potentials characteristic of slow changes in the frequency of a modulated carrier wave and characteristic of changes in the frequency of said carrier wave at syllabic frequency, a first resistance and condenser in a circuit excited by said potentials, said first resistance and first condenser forming a time constant network of a time duration appropriate for said slow changes, a second resistance and second condenser in series in shunt to a part at least of said first resistance, said second resistance and second condenser forming a time constant network appropriate for said syllabic changes, and output connections to said second resistance and first condenser.

10. In an angular velocity modulation system a network for transferring, from one point to another, potentials characteristic of slow changes in the frequency of a modulated carrier wave and characteristic of changes in the frequency of said carrier wave at syllabic frequency and modulation frequency, a first resistance and condenser in a circuit excited by said potentials, said first resistance and first condenser forming a time constant network cf a time duration appropriate for said slow changes, a second resistance and second condenser in series in shunt to a part at least of said first resistance, said second resistance and second condenser forming a time constant network appropriate for said syllabic changes, a third resistance and third condenser in series in shunt to a part at least of said second resistance, said third resistance and third condenser forming a time constant network appropriate for said modulation frequency and output connections to said third resistance and first condenser.

11. A system as recited in claim 9, wherein said resistances are adjustable.

12. Ina network for transferring, from one point to another, potentials characteristic of slow changes in the frequency of a modulated carrier wave and characteristic of changes in the frequency of said carrier wave at syllable frequency due to modulation thereof in a carrier stabilized timing modulation system of the reaotance tube type, a first resistance and condenser in a circuit excited by said potentials, said first resistance and first condenser forming a time constant network of a time duration appropriate for said slow changes, a second resistance and second condenser in series in shunt to a part at least of said first resistance, said second resistance and second condenser forming a time constant network appropriate for said syllabic changes, and

connections for coupling said second resistance and first condenser to electrodes of said reactance tube.

13. In a network for transferring, from one point to another, potentials characteristic of slow changes in the frequency of a modulated carrier wave and characteristic of changes in the frequency of said carrier wave at syllabic frequency due to modulation thereof in a carrier stabilized timing modulation system of the reactance tube type, a first resistance and condenser in a circuit excited by said potentials, said first resistance and first condenser forming a time constant network of a time duration appropriate for said slow changes, a second resistance and second condenser in series in shunt to a part at least of said first resistance, said second resistance and second condenser forming a time constant network appropriate for saidsyllabic changes, a third resistance and a third condenser in series in shunt to a part at least of said second resistance, said third resistance and third condenser forming a time constant network appropriate forsaid modulation frequency and connections for coupling said third resistance and first c'ondenser to electrodes of said reactance tube.

14. In a signalling system, a tuned circuit wherein wave energy the wave length of which is to be controlled flows, at reactance tube coupled to said tuned circuit to control the tuning thereof and thereby control the wave length of the wave energy flowing therein, connections for modulating the conductivity of said reactance tube in accordance with signals to correspondingly control the wave length of the wave energy, means for deriving potentials characteristic of slow changes, and syllabic changes, and a resistive and capacitive network for simultaneously applying said derived potentials to said reactance tube.

15. In a signalling system, a tuned circuit wherein wave energy the wave length of which is to be controlled flows, a reactance tube coupled to said'tuned circuit to control the tuning thereof and thereby control the wave length of the wave energy flowing therein, connections for modulating the conductivity of said reactance tube in accordance with signals to correspond- 

